See that little frog at the top of this post? Consider him the canary in the coal mine.
As humans continue burning coal, invading wetlands, and spraying herbicides like atrazine, we are throwing off the balance of predator, prey, and parasite in nature, beginning a chain reaction that could rapidly wipe out many species.
From Scientific American:
The northern leopard frogs that inhabit the boreal U.S. have never recovered from some catastrophic population declines in the 1970s. Some blame it on the acidifying lakes and streams caused by coal-burning, others point to the ongoing loss of wetlands to development, and now new evidence shows that the herbicide atrazine—widely sprayed on crop fields throughout the region—is killing the frogs by helping parasitic worms that feast on them.
“Atrazine provides a double whammy to frogs: It increases both amphibian exposure and susceptibility,” says biologist Jason Rohr of the University of South Florida in Tampa, who tested the impact by re-creating field conditions in 300-gallon (1,135-liter) tanks in his lab. “Atrazine is one of the more mobile and persistent pesticides being widely applied. In fact, residues have been found in remote, nonagricultural areas, such as the poles.”
That may explain why amphibians are on the decline worldwide. As many as one third of the nearly 6,000 known amphibian species—frogs, toads, salamanders, even wormlike caecilians—are threatened with extinction, according to the International Union for Conservation of Nature (IUCN). And no one knows why.
In the case of the northern leopards, the culprit appears to be the common herbicide acting as a double-edged sword: It suppresses the frogs’ immune systems while boosting the population of snails that play host to parasitic worm larvae, the latter of which infect the weakened leopard frogs.
Such herbicides are present in 57 percent of U.S. streams, according to the U.S. Geological Survey, and it is that water pollution—not inbreeding—that is the prime suspect in the high rate of deformity in U.S. amphibian populations, according to new research from Purdue University.